Mickelson became golf's oldest major champion last month, capturing his sixth major title.

LA JOLLA (AFP) - Phil Mickelson has spent the weeks since his historic PGA Championship victory re-learning the nuances of a once-familiar hometown Torrey Pines layout in quest of an elusive US Open title.

The American left-hander, a record six-time US Open runner-up who turns 51 on Wednesday, has won three PGA titles at Torrey Pines, where the 121st US Open tees off Thursday.

But none of his youthful triumphs on the oceanside course came since its 2001 renovation.

"When the course was redesigned, all that local knowledge went away," Mickelson said Monday. "I really haven t come out here and spent a ton of time.

"I really made an effort, having the last week off, to spend time out here and really re-learn the greens. I spent a lot of hours on the greens last week to see if I can get that local knowledge again.

"I m playing well and I just wanted to give myself every opportunity to play at my best."

Mickelson became golf s oldest major champion last month, capturing his sixth major title with a stunning victory at Kiawah Island.

"The game just started to feel easy again," Mickelson said. "It s exciting to be able to put it together when nobody expects it.

"I m hopeful some of the things I learned will carry over and give me some more opportunities, because I feel like I m playing some good golf."

With a victory this week at Torrey Pines, Mickelson would become the sixth player to complete a career Grand Slam, joining Tiger Woods, Jack Nicklaus, Gary Player, Ben Hogan and Gene Sarazen.

"It s a unique opportunity because I ve never won a US Open. It s in my backyard. I have a chance to prepare properly and I wanted to put in the right work.

"So I ve kind of shut off all the noise. I ve shut off my phone. I ve shut off a lot of the other stuff to where I can focus in on this week and really give it my best chance to try to play my best."

Another ageless wonder -- 43-year-old Tom Brady, a seven-time NFL champion and the oldest quarterback to win a Super Bowl crown -- has been an inspiration to Mickelson as well as a partner in made-for-TV golf events.

"I learn a lot by just watching and observing the dedication, the hard work. It s inspiring," Mickelson said. "When you see it happen, it s much easier to do."

Mickelson s epic history of US Open near-misses, the most recent in 2013 to England s Justin Rose at Merion, might be negated by San Diego being his hometown.

Mickelson finds he can go home again and he s going to school on revamped Torrey Pines to try and avoid past mistakes.

"I haven t spent a lot of time learning the nuances," Mickelson said. "I put a lot of time in on the greens... I needed to relearn and see the breaks and know what the ball does on these greens.

"I ve just tried to do too much in the past. I felt like if I could learn the greens... that will hopefully allow me to play a little bit more stress free so I m not trying to take on too much."

Mickelson warns that lightning-fast greens will require discipline from the bunkers and firm contoured fairways will be tough to reach.

"It s going to be a difficult test," he said. "But it seems like the setup is pristine and it s going to be a fun, fair and difficult challenge."

Mickelson will be the oldest in the field of 156 at the 7,652-yard, par-71 layout, where crowds between 8,000 and 10,000 are expected daily, limited due to Covid-19 safety issues.

It s the second US Open to be staged at Torrey Pines, the first since Tiger Woods, playing on a broken leg, beat Rocco Mediate in a playoff for the 2008 crown.

Woods, a 15-time major winner, remains sidelined while recovering from severe leg injuries suffered in a February car crash.

Nine different players have won the past nine major titles, a run that began with Woods capturing the 2019 Masters.